Method and device for cleaning support elements in printers or copiers by means of magnetic fields

ABSTRACT

The invention relates to a method and devices for cleaning the surfaces of applicator rollers, photoconductor drums, transfer belts, and photoconductor belts using magnetic roller systems. The invention also relates to methods and systems for cleaning magnetic rollers to whose surfaces toner particles adhere. In a first embodiment, a squeegee/scraper is disposed at a distance to the surface of the roller. In another embodiment, a magnetic stator configuration with two spaced apart magnetic elements is used whose poles have substantially the same active direction.

BACKGROUND OF THE INVENTION

The invention concerns an electrophotographic print or copy device inwhich a toner application unit applies electrically charged tonerparticles to the surface of a first carrier element. At least one partof the applied toner particles is transferred from the first carrierelement to a second carrier element. A cleaning unit removes remainingtoner particles from the first carrier element. A further aspect of theinvention concerns a device to clean a roller of toner particles in anelectrophotographic printer or copier, on whose surface is conveyed aparticle mixture made up of electrically charged toner particles andferromagnetic carrier particles. Furthermore, methods to operate anelectrophotographic printer or copier and to clean a roller in anelectrophotographic printer or copier are specified.

In electrophotographic printers or copiers, image development methodsare used that develop electrostatic charge images on surfaces (forexample, charge images on a photoconductor) over an air gap or in directcontact with triboelectrically charged toner that is located on asurface of an applicator element. Such an applicator element can, forexample, be implemented as a roller or as a continuous band. The tonerparticles are triboelectrically charged before the transfer to theapplicator element. In known printers or copiers, a two-componentmixture made of toner particles and ferromagnetic carrier particles isgenerated. The two-component mixture is mixed in the printer or copiersuch that the toner particles rub on the carrier particles, whereby theyare triboelectrically charged.

It is known to ink surfaces with toner particles that are comprised in atwo-component mixture. A magnetic roller arrangement transports thetwo-component mixture in an area with slight separation between themagnetic roller arrangement and the surface to be inked, whereby amagnetic field of a magnet element acts on the two-component mixture. Inthis area, a magnetic brush is fashioned that comprises carrierparticles and toner particles, whereby only the latter is transferred tothe surface to be inked. The carrier particles are held back due to themagnetic field.

In other known printers or copiers, the transfer of the toner particlesfrom the magnetic roller arrangement to the applicator element ensuesover an air gap between the magnetic roller and the applicator elementthat is not completely bridged by the accumulation of the two-componentmixture. The transfer of the toner particles to the applicator elementsurface can be supported by an auxiliary transfer voltage, meaning by apotential different between magnetic roller and applicator element.

During an image development event, the toner is transferred via an airgap or via direct contact from the applicator element surface to thesurface bearing a charge image (for example, to the surface of aphotoconductor drum or a photoconductor band), corresponding to a chargedistribution of a latent charge image. Corresponding to the latentcharge image, toner particles remain on the surface of the applicatorelement in the form of an image negative of the developed charge image.The toner particles remaining on the applicator element must be removedfrom the applicator element before a new application of a closedhomogenous toner layer on the applicator element. The unprinted surfaceof a print page with text is approximately 95% of the total surface.Given printing of such an average print page, approximately 95% of thetoner particle quantity applied to the applicator element must thus beremoved from it. Depending on the type of print image to be inked, 0 to100% of the toner particle quantity must be removed from the applicatorelement.

In print systems with high print speed, the cleaning of the applicatorelement only insufficiently ensues with the aid of known cleaningdevices. After multiple applications of toner particles on theapplicator element, and after incomplete cleaning of the toner particlesremaining on the applicator element after the inking of the latentcharge image, these form a non-uniform thick layer on the applicatorelement. The inhomogeneous toner layer of different thickness can causeprint image interferences, such as “memory effect”. Given memory effect,the preceding print image is visible in inked regions of the print imageas a result of the inhomogeneous toner layer on the applicator elementthat is transferred as a print image onto a medium to be printed. For aqualitatively high-grade print, a complete removal of the remainingtoner particles is therefore necessary before the new application oftoner onto the applicator element.

If, given a photoconductor drum, the latent charge image is developed,meaning inked with toner particles corresponding to the chargedistribution, and the toner image is transfer printed onto a carriermaterial, some residue of the toner image remains on the surface of thephotoconductor drum. This toner residue must be removed from this beforethe new application of a latent charge image on the photoconductor drum.

It is likewise necessary in print or copy devices to remove tonerparticles from photoconductor bands, transfer bands and magnetic rollersin order to not affect the electrophotographic process and to ensure ahigh print quality.

In known print or copy devices, the cleaning (meaning the removal oftoner residues) of photoconductor drums ensues with the aid of plasticbrushes that have direct contact with the surface of the photoconductordrum. Wear thereby ensues both on the plastic brushes themselves and onthe photoconductor drum. Furthermore, the toner particles to be removedare subject to a significant mechanical stress during the cleaningprocess with such brushes, whereby the physical properties of the tonerparticles are negatively changed.

From U.S. Pat. No. 4,383,497, an arrangement for cleaning an applicatorelement is known in which the toner particles are mechanically strippedfrom the applicator element with the aid of a stripping blade that is indirect contact with the surface of the applicator element. The tonerparticles are thereby mechanically significantly stressed, meaning highmechanical pressure and shear forces are exerted on the toner particles.The mechanical stress of the toner particles leads to a negative changeof the physical properties, or even to a loss of functionality of thetoner material, whereby print image interferences can ensue given areuse of these toner particles to develop subsequent print images. Suchblades are, for example, produced from plastic, metal or from metalcoated with ceramic. The direct contact between blade and applicatorelement above all effects a high wear in the blade. The wear isdifferent in regions of the blade, whereby a non-uniform cleaning of thestructure element ensues given a worn blade. This blade must beexchanged frequently in high-capacity printing systems. Moreover, thesurface of the applicator element can be damaged by the mechanicalfriction between blade and applicator element. Such damage canaltogether impair the function of the applicator element.

From German Patent Document DE 41 05 261 A1, an image generation devicewith two identical image generation units is known. A first imagegeneration unit is arranged in a development position and operates as adevelopment unit. The second image generation unit is arranged in acleaning position and operates as a cleaning unit. The image generationunits are alternatively and repeatedly brought into the developmentposition and the cleaning position. The particle mixture comprised in animage generation device is thereby used for application of tonermaterial and, at another point in time, for cleaning.

From U.S. Pat. No. 4,141,165, an electrostatic copier is known in whichmagnetic brushes are used to ink a charge image of a photoconductor drumand to remove residual toner from the photoconductor drum. A roller thatinternally comprises stationary magnets is used for application andcleaning. The magnetic brushes are generated with the aid of themagnets. A particle mixture is removed from the surface of the rollerwith the aid of scrapers whose edges scrape on the surface of theroller.

A magnetic brush cleaning device for a copy device is known from GermanPatent Document DE 32 46 940 A1. With the aid of a magnetic brushdevice, it is achieved that a mixture made of a magnetic carrier and thetoner glides over the surface of a photoconductor and absorbs tonerresidue adhering to the photoconductor surface. The cleaned toner issupplied with the aid of a toner recovery device that comprises aplurality of rollers. Toner material adhering to the rollers of thetoner recovery device is removed from these with the aid of scrapersscraping on the rollers.

From German Patent Document DE 32 41 819 C2, a magnetic brush cleaningdevice is known in which a cleaning roller is provided in which internalstationary magnets are provided that generate magnetic brushes. Themagnetic brushes slip over the surface of a photoconductor drum andclean off residual toner from it that remains after the transferprinting of a toner image on the control device. The cleaned-off tonermaterial is transferred from the magnetic roller to a second roller.With the aid of a stripper that lies on the surface of the secondroller, the toner material is scraped from the surface of the secondroller.

From Japanese Patent Document JP 2000267397 A, magnetic rollers areknown that are used to ink a charge image of a photoconductor drum andto clean off residual toner from the photoconductor drum. Two abuttingmagnet elements that are arranged opposite the surface of thephotoconductor drum prevent the contact of the magnetic brushes with thesurface of the photoconductor drum. The magnets of the magnetic rollerrotate with the magnetic roller.

From German Patent Document DE 32 49 767, a cleaning device is known forthe removal of developer particles from an imaging surface of a moving,photoconductive band in an electrophotographic copier device. The backside of the band is also cleaned of possible toner residues and dustdeposits with the aid of this cleaning device. The band is pressedagainst a cleaning roller with the aid of a stripper. Via magnetsarranged in the cleaning roller, the stripper is pressed against thecleaning roller by means of a plate made from a magnetizable material.

From German Patent Document DE 39 40 079 C2, a method is known to removea thin layer from a movable photoconductive part of an image generationdevice. Toner material that is located on a roller surface is therebyremoved with the aid of a stripper that scrapes the toner material fromthe roller surface.

SUMMARY OF THE INVENTION

It is the object of the invention to specify electrophotographic printor copy devices, as well as methods for operation of electrophotographicprint or copy devices, in which a high print quality is achieved,whereby a low stress of the particle mixture made of ferromagneticcarrier particles and electrically charged toner particles ensues.Furthermore, devices and methods are specified for cleaning a roller inan electrophotographic printer or copier that ensure a maintenance-freeoperation of the devices for cleaning.

This object is achieved for an electrophotographic print or copy devicewith the features as described below.

Various embodiments of the invention are described in the followingparagraphs. With the aid of an embodiment of the inventive device, tonerparticles applied to the surface of a roller of an electrophotographicprinter or copier are reliably removed with little effort. Inside theroller, two magnet elements are arranged stationary, of whichrespectively one pole is directed towards the roller surface such thatthey act approximately in the same direction. Viewed in the rotationdirection of the roller, the magnet elements are arranged at a distancefrom one another such that the carrier particles remain on the magnetelements, and raised accumulations (what are known as “magneticbrushes”) form, whereby, given a rotation movement of the roller, thecarrier particles rub on its surface. The cleaning device reliablyremoves the toner particles adhering to its surface and requires noadditional space in the electrophotographic printer or copier since themagnet elements are arranged inside the roller.

The device operates without wear and effects an additional triboelectriccharge of the toner. Additional energy is not required to operate thedevice. Furthermore, the device is suitable for various particlemixtures made of up toner particles and carrier particles. The cleaningalso reliably ensues given a change of the physical properties of aparticle mixture used in a print or copy device. With increasingduration of use, such changes ensue via mechanical stress of the tonerparticles.

The adjacent poles of both magnet elements facing the particle mixtureare similar, meaning the magnetic fields of these poles act inapproximately the same direction, such that a low field strength ispresent between the magnet elements on the roller surface. The fieldvectors of the magnetic fields have an opposite sense of direction inthis region on the roller surface, such that no resulting field strengthis present there given approximately uniform magnet elements. Theparticle mixture on the roller surface remains on the magnet elementsand forms raised accumulations in which a rotating roller-shapedmovement is generated within the particle mixture given a rotationmovement of the roller. Given this motion, the particle mixture abradesthe toner particles adhering to the roller surface.

In an advantageous embodiment of the device, the magnet elements arearranged such that at least one part of the carrier particles in asub-region between the two magnet elements is loosened from the rollersurface by the force of the magnetic fields of the magnet elementsacting on the carrier particles, whereby the particle mixture isparticularly well swirled in the region of the magnet elements given arotation movement of the roller. It is thereby achieved that tonerparticles that are located on the roller surface are loosened from thisand completely rubbed off, whereby the mechanical stress of the particlemixture is low. The physical properties of the particle mixture remainthe same. In this embodiment, the toner particles electrostaticallyapplied to the outer circumferential surface of the roller can beparticularly effectively removed. Given a rotation movement of theroller, carrier particles are conveyed back in the areas on the rollersurface, whereby a part of the particle mixture remaining in these areasis also conveyed. The abraded toner particles are also transported awaywith this particle mixture, such that an exchange of the remainingparticle mixture ensues.

It is also advantageous to align the axes of the poles of the magnetelements radially relative to the rotation axis, since a maximal fieldeffect of the magnet elements arranged in a static manner (i.e.,stationary) inside the roller is thereby achieved on the carrierparticles.

In another embodiment of the invention, in addition to the magnetelements, a scraper is arranged at a predetermined separation from theroller surface. It is thereby advantageous to arrange the scraper in therotation direction of the roller after the first and second carrierelement, near the second magnet element. It is also advantageous toarrange the scraper in the lower roller half. The swirling of theparticle mixture to abrade the toner particles from the surface of theroller, and the separation of the particle mixture from the rollersurface, ensues effectively and with low design cost via the arrangementof the scraper.

In another advantageous embodiment, the outer circumferential surface ofthe roller has a roughness in the range of 1 to 5000 μm. The roughnessof the roller surface can be cost-effectively produced with a highquality via flame spraying, whereby a layer is generated that comprisesaluminum, chromium, nickel, copper, conductive plastic and/or a plasticwith a conductive layer. The surface of the roller can thereby becharged with a set potential in order to, for example, support thetransfer of toner particles onto this roller or from this roller.Rollers and surfaces can also be produced from these materials simplyand cost-effectively.

It has proven to be particularly advantageous to arrange the adjacentedges of both magnet elements at a distance in the range of 0.01 to 10mm, since a particularly thorough cleaning ensues at this distance. Thisdistance range is, however, dependent on the field strength of themagnet elements used, on the circumferential speed of the roller, on theparticle mixture used, most of all on the carrier particles used, and onthe distance between the magnet element and the outer circumferentialsurface of the roller. The cleaning device can be simply adapted to theoperating conditions of the printer or copier by changing the distancebetween the magnet elements and/or by the use of magnet elements withother field strengths.

The roller used in this cleaning device can comprise further magnetelements to generate particle accumulations, what are known as magneticbrushes, on the roller surface. In further advantageous embodiments, themagnet elements are permanent magnets. This is particularly advantageoussince, in contrast to electromagnets, no auxiliary energy is necessaryfor permanent magnets.

A thorough and wear-free cleaning of the roller ensues via an inventivemethod to clean a roller in an electrophotographic printer or copier. Nofurther additional aggregates are necessary for cleaning, whereby noadditional space for the cleaning device is needed for cleaning. Thetoner particles are additionally triboelectrically charged by thecleaning process. The cleaning of the roller ensues almost without wear.

A second aspect according to an embodiment of the invention concerns anelectrophotographic print or copy device as well as an inventive methodto operate an electrophotographic print or copy device. A first carrierelement is inked with toner, whereby this carrier element issubsequently cleaned of toner residues with the aid of a rollerarrangement of a cleaning unit. The toner residues are removed from thisroller arrangement with the aid of a scraper magnet element arrangement.It is thereby prevented that toner particles are permanently applied tothe surface of the roller arrangement and form a crust-like layer thatprevents electrostatic effects, and thus impairs the electrophotographicprocess. In the inventive device, and given the inventive method, theelectrophotographic print or copy event can be implemented in highquality and with high speed. Such an electrophotographic print or copydevice can be cost-effectively produced via the simple, compact design.

According to a third aspect according to an embodiment of the invention,a device is specified for cleaning a roller in an electrophotographicprinter or copier. This device has a scraper that is arranged at adistance from the surface of a roller on whose roller surface isconveyed a particle mixture made up of carrier particles andelectrically charged toner particles. A magnet element is statically(i.e., stationary, with regard to the scraper) arranged inside theroller, such that the carrier particles in the area (viewed in therotation direction of the roller) before the scraper form a raisedaccumulation, i.e., a magnetic brush, on the roller surface. Given arotation movement of the roller, the carrier particles of theaccumulation abrade on its surface. Via this device, it is simplypossible to achieve a high degree of cleaning of the roller to becleaned. Such a device is simple and cost-effective to produce. The wearof the cleaning elements and the roller have been significantly reducedwith regard to known cleaning devices for rollers.

In another embodiment of the invention, the scraper strips off at leastone part of the particle mixture located on the roller. The magneticfield of the magnet element holds parts of the particle mixture strippedby the scraper in the area in front of the scraper. Via the rotationmovement of the roller and via the scraper in a fixed position, theparticle mixture is swirled in the area in front of the scraper.

It is thereby achieved that toner particles that are located directly onthe roller surface are also mechanically abraded from the surface of theroller, primarily via the swirling of the carrier particles. The abradedcarrier particles are absorbed by the particle mixture in the area infront of the scraper. Carrier particles that are located directly on thesurface of the roller are thereby also loosened by these and can thus beeffaced. The negative change of physical properties of the roller via acrust-like layer made of toner particles on the roller surface is thussimply and cost-effectively prevented. A layer made of toner particleson the roller surface has an electrically insulating effect and limitsthe effect of a potential difference between the roller surface andfurther elements such as further rollers and bands of the printer orcopier, the use of the abraded carrier particles prevents this effect.Such potential differences are, for example, used to transferelectrically charged toner particles in printers or copiers.

Furthermore, it is advantageous to align the axes of the poles of themagnet element radially relative to the rotation axis of the rollerarrangement. There are thereby areas with higher magnetic field strengthin which raised accumulations made of toner particles and carrierparticles form on the surface of the roller. It is also advantageous toarrange in a stationary manner a plurality of magnet elements inside theroller. The axes of the poles are respectively radially aligned, wherebythe poles of neighboring magnet elements are aligned approximatelyopposite. It is thereby achieved that a strong magnetic field isgenerated between neighboring magnet elements.

If, in another embodiment, the scraper is arranged in the lower rollerhalf, the particle mixture can simply fall down onto the scraper. Thetransportation of the particle mixture away onto the scraper is thussimply possible. The particle mixture falling down can, for example, becollected in a catch reservoir arranged under the roller, or falldirectly into what is known as a mixture sump of the printer or copierin which the two-component mixture is located, and subsequently can besupplied again to the electrophotographic print or copy process.

In a further embodiment, the outer circumferential surface of the rollerhas a roughness in the range of 1 to 5000 μm. It is thereby achievedthat the particle mixture to be transported onto the roller surface hasan adhesion sufficient for the transport, and that the particle mixturecan be removed again from the surface in a simple manner. Additionallyor alternatively, the surface roller can be profiled in order to reducea slip of the particle mixture on the roller surface and to ensure acontinuous transport of the particle mixture given a rotation movementof the roller.

It is advantageous to generate the surface of the roller with the aid ofa flame spray method. With the aid of the flame spray method, a surfaceof the roller can be simply and cost-effectively produced with asuitable roughness. If the roller surface and/or at least one part ofthe rotating hollow roller is produced from aluminum, chromium, nickel,copper, conductive plastic and/or a plastic with a conductive layer, thesurface of the roller can be charged with a set potential in order to,for example, support the transfer of toner particles onto this roller orfrom this roller. Rollers and surface can also be produced from thesematerials simply and cost-effectively.

In an advantageous development of the invention, the distance betweenscraper and roller surface is set in the range of 0.05 to 6 mm. Such adistance ensures a low wear of scraper and roller as well as a reliablecleaning of the roller toner particles fixed on the roller surface.

Via the inventive method for cleaning a roller in an electrophotographicprinter or copier, it is achieved that the cleaning of the rollerthoroughly ensues with little effort. Additional auxiliary energy is notnecessary for this. Furthermore, a compact design of the printer orcopier is possible with the aid of the method, whereby the method can beimplemented almost without wear for the roller and for the scraper viathe separation between scraper and roller surface. This method forcleaning the roller can be used for various particle mixtures made up oftoner particles and carrier particles. The cleaning effect of such anarrangement also persists when the physical properties of the particlemixture change.

A fourth aspect according to an embodiment of the invention concerns aelectrophotographic print or copy device in which a toner applicationunit applies electrically charged toner particles to the surface of afirst carrier element. At least one part of the toner particles istransferred from the first carrier element to a second carrier element.A cleaning unit removes from the first carrier element the tonerparticles remaining on the first carrier element after the transfer, Thecleaning unit comprises a roller that is arranged at a distance from thefirst carrier element. At least two magnet elements are arranged in astationary manner inside the roller. A particle mixture that compriseselectrically charged toner particles and ferromagnetic carrier particlesis conveyed on the surface of the roller. The adjacent poles of bothmagnet elements facing the particle mixture are uniformly (viewed in therotation direction of the roller) arranged at a distance relative to oneanother, such that the carrier particles on the surface of the rollerform at the magnet elements at least one accumulation whose carrierparticles, given a rotation movement of the roller, abrade on itssurface.

With the aid of the inventive electrophotographic print or copy device,and given a method to operate this electrophotographic print or copydevice, it is possible with little effort to produce qualitativelyhigh-grade print images in a simple manner, whereby the mechanicalstress of the toner is relatively low. Via the cleaning of the firstcarrier element and the roller arrangement used for cleaning, aqualitatively high-grade print image is also ensured given longer use ofthe print or copy device, whereby toner particles that adhere to thesurface of the roller are abraded from this via a magnet elementarrangement by the particle mixture on the surface of the roller. It isthereby prevented that toner particles on the surface of the roller arepermanently applied, hinder the electrostatic events, and thus impairthe electrophotographic process. The physical properties of the rollerarrangement and of the toner mixture can be kept constant over a largespan of time via the device or the method.

In an advantageous embodiment, a scraper is arranged stationary at apredetermined distance from the roller surface in the area of the secondmagnet element or, viewed in the rotation direction of the roller, afterthe two magnet elements. The roller-shaped movement within the particlemixture made up of carrier particles and toner particles in the regionof the magnet elements on the roller surface is intensified by thescraper, whereby in the area in front of the scraper, at least parts ofthe toner particles that have stuck to the roller surface are abradedand loosened from this.

A fifth aspect according to an embodiment of the invention concerns anelectrophotographic print or copy device as well as a method to operatesuch an electrophotographic print or copy device. Theelectrophotographic print or copy device has a toner application unitthat transfers toner particle onto a first carrier element with the aidof a particle mixture made up of electrically charged toner particlesand ferromagnetic carrier particles. After the transfer of at least onepart of the toner particles of the particle mixture, the particlemixture is supplied to a second carrier element of a cleaning unit. Withthe aid of the supplied particle mixture, the cleaning unit absorbs thetoner particles present on the first carrier element.

In an embodiment of the invention, an applicator element is used as afirst carrier element and a photoconductor is used as a second carrierelement. It is thereby achieved that the applicator element is inkedwith toner particles with the aid of the toner application unit, wherebya part of the toner particles are transferred from the applicatorelement onto the photoconductor, corresponding to the latent chargeimage located on the photoconductor, and the toner particles remainingon the applicator element are removed from this. A uniform layerthickness of the toner particles of the print image is ensured via thecombination of the applicator element and the photoconductor, wherebyqualitatively high-grade, homogenous print images are generated with auniform print intensity.

In another development of the invention, the first carrier element is aphotoconductor and the second carrier element is a carrier material tobe printed or a transfer element. The photoconductor is inked with tonerparticles corresponding to its latent charge image and the toner imageis transfer printed onto the carrier material to be printed or thetransfer element. The toner particles remaining after the transferprinting onto the photoconductor are removed from the photoconductorwith the aid of the cleaning unit. It is thereby achieved that thephotoconductor is completely cleaned of toner particles after a print orcopy event, before a further print or copy event, and memory effects areprevented in the subsequent print image.

In a further embodiment of the invention, the rotation direction of theroller is the same as the rotation direction of the first carrierelement. With regard to an opposite rotation direction of the rollerrelative to the movement direction of the first carrier element, thecleaning effect is increased since, with the aid of the roller, moreferromagnetic carrier particles for absorption of toner particles aredirected to the first carrier element, said ferromagnetic carrierparticles contacting the surface of the first carrier element andremoving the toner particles adhering to it. The carrier particles thatare located on the surface of the roller are rotated together with theroller, and thus transported in its circumferential direction via therotation movement of the roller. A rough and/or structured rollersurface aids this transport of the carrier particles.

In an advantageous embodiment of the invention, the axes of the poles ofthe magnet element are aligned radially relative to the rotation axis ofthe roller. It is thereby achieved that the magnetic field of the magnetelement exerts a particularly large force on the ferromagnetic carrierparticles in the area in which the pole of the magnet element facing thecircumferential surface of the roller has a slight distance from theroller surface. Via this force, the carrier particles are aligned on thefield lines of the magnet element and temporarily held at least in partin this area, such that a raised accumulation, what is known as amagnetic brush, is formed via the concentration of the carrier particlesand their alignment. The distance between carrier element and roller ispreferably smaller than or equal to the height of the magnetic brush onthe roller. The distance between the roller and the first carrierelement is preferably set in the range between 0.1 and 7 mm.

In a further embodiment of the invention, it is also possible that thequantity of the ferromagnetic carrier particles conveyed on the surfaceof the roller comprises a predetermined proportion of toner particles,whereby a particle mixture made up of carrier particles and tonerparticles is used for cleaning the roller. Particle mixtures made up ofcarrier particles and toner particles that have been previously used,for example, to ink a carrier element, can thus be used for cleaning.The toner application unit transfers toner particles of a two-componentmixture made up of electrically charged and ferromagnetic carrierparticles to the first carrier element. This two-component mixture issupplied to the roller of the cleaning unit after the transfer of atleast one part of the toner particles to the first carrier element. Theparticle mixture supplied to the cleaning unit absorbs the tonerparticles remaining on the first carrier element. It is thereby achievedthat the particle mixture must only be prepared once in theelectrophotographic print or copy device. It is first used for tonerapplication and subsequently for cleaning.

In another embodiment, the particle mixture is transferred from thetoner application unit for cleaning of at least one magnet element withthe aid of a magnetic field. Via the force of the magnetic field on theferromagnetic carrier particles, these are transported from the tonerapplication unit to the cleaning unit together with the toner particleslocated with the ferromagnetic carrier particles.

Alternatively, or in addition to this, the transfer of the particlemixture from the toner application unit to the cleaning unit can ensuewith the aid of a guide element arranged between the toner applicationunit and the cleaning unit. Such a guide element can, for example, be aguide sheet or a conveyor device such as a transport band or a screwconveyor. It is thereby ensured that the particle mixture iscontinuously transferred from the toner application unit to the cleaningunit.

If permanent magnets are used as magnet elements, no energy supply isnecessary for the magnet elements. Furthermore, permanent magnets areinexpensive and can be produced in nearly arbitrary forms. The side ofthe magnet elements facing the surface of the roller can thereby, forexample, by implemented curved, such that the structure of the rollerarrangement can be designed more compact. If a plurality of magnetelements whose poles are respectively aligned approximately radiallyrelative to the rotation axis are arranged inside the roller, aplurality of magnetic brushes can thus be formed on the surface of theroller with the aid of these magnet elements. The transfer of tonerand/or carrier particles can thus ensue simply, cost-effectively andwithout wear in the print or copy device.

In another advantageous embodiment of the invention, a first potentialdifference is generated between the toner application unit and the firstcarrier element, and/or a second potential difference is generatedbetween the cleaning unit and the first carrier element. It is therebyachieved that the transfer of the toner particles from the tonerapplication unit to the first carrier element or from the first carrierelement to the cleaning unit ensues in a simple manner. With the aid ofthe potential differences, a simple transfer of the toner particles iscost-effectively possible between various elements with little designeffort. The removal of the toner particles from the first carrierelement is supported by this potential difference, whereby all tonerparticles are completely removed from the carrier element.

In an inventive method for operation of an electrophotographic print orcopy device, the generation of qualitatively high-grade print images issimply and cost-effectively possible. The application of toner particlesto carrier elements and the cleaning of the carrier elements with theaid of magnetic rollers ensues nearly without wear according to theinventive method.

DESCRIPTION OF THE DRAWINGS

For better understanding of the present invention, reference is made inthe following to the preferred exemplary embodiments shown in thedrawings that are described using specific terminology. However, it isto be noted that the scope of protection of the invention should notthereby be limited, since such changes and further modifications to theshown devices and/or to the method, as well as such further applicationsof the invention as they are shown therein, are viewed as typicalpresent and future expert knowledge of a competent average man skilledin the art. The Figures show exemplary embodiments of the invention.

FIG. 1 is a pictorial side view of an arrangement to apply and removetoner to or from an applicator element surface, whereby a particlemixture made up of ferromagnetic carrier particles and electricallycharged toner particles serves for application and for removal;

FIG. 2 is a pictorial side view of a further arrangement to apply andremove toner, similar to the arrangement shown in FIG. 1;

FIG. 3 is a pictorial side view of the arrangement from FIG. 1, wherebyelectrical potentials of the roller surfaces are shown;

FIG. 4 is a pictorial side view of an arrangement to clean an applicatorelement with the aid of a magnetic roller arrangement, whereby ascraper-magnet element device serves for cleaning of the magnetic rollerarrangement;

FIG. 5 is a pictorial side view of an arrangement to develop a latentcharge image on a photoconductor drum with the aid of a magnetic rollerarrangement, as well as a scraper-magnet element device to clean themagnetic roller arrangement;

FIG. 6 is a pictorial side view of an exemplary embodiment for theconfiguration of the magnet stator and the scraper, in which the surfaceof the magnetic roller arrangement is cleaned of toner particles;

FIG. 7 is a pictorial side view illustrating the movements within theparticle mixture in the area of the magnetic roller in the arrangementshown in FIG. 5;

FIG. 8 is a pictorial side view of an arrangement to remove tonerparticles from a magnetic roller with the aid of a magnet arrangementmade up of two magnet elements, whereby the magnetic roller serves forthe removal of a homogenous toner layer on an applicator roller;

FIG. 9 is a pictorial side view of an arrangement to remove tonerparticles from a magnetic roller with the aid of a magnet arrangementmade up of two magnet elements, whereby the magnetic roller serves todevelop a latent charge image on a photoconductor;

FIG. 10 is a pictorial side view of an exemplary embodiment for theconfiguration of the magnet stator of the roller system from FIG. 9 toachieve the cleaning effect on the roller surface;

FIG. 11 is a pictorial side view of the formation of magnetic brushes onthe magnet elements, as well as the movements within the particlemixture on the roller surface that are indicated by the arrows next tothe mixture;

FIG. 12 is a flux density graph illustrating the field distribution inthe magnetic near field directly on the roller surface of the magneticroller system shown in FIG. 10; and

FIG. 13 is a flux density graph illustrating the field distribution inthe magnetic far field at the distance of approximately 9 mm from theroller surface of the magnetic roller system shown in FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An arrangement 10 for toner application on an applicator roller 12 withthe aid of a first magnetic roller arrangement 14 is shown in FIG. 1,whereby a particle mixture made up of electrically charged tonerparticle and ferromagnetic carrier particles, a “two-component mixture”,is used to apply the toner on the applicator roller 12. Such anapplicator roller 12 serves to transport toner particles in a printer orcopier. In the following, the toner particles are also generallydesignated as toner. Applicator rollers 12 are in particular used todevelop a latent charge image on a photoconductor element 13 with toner,whereby the surface of the applicator roller 12 is provided with auniform toner layer 36. The uniform toner layer 36 is directed to thelatent charge image of the photoconductor element 13, whereby the tonerlayer 36 is transferred from the applicator roller 12 to thephotoconductor element 13 in the areas of the latent charge image to beinked.

To transfer toner particles to the surface of the applicator roller 12,a “magnetic brush” 18 is formed from the two-component mixture betweenthe first magnetic roller arrangement 14 and the applicator roller 12.Located on a stator 26 inside a rotatable, hollow roller 24 of thearrangement 14 are oblong magnet elements 28, 30, 32, 34 whose poles arealternately directed outwards (viewed in the circumferential direction).The ferromagnetic carrier particles are arranged and aligned at eachmagnet element 28, 30, 32, 34 by the force effect of the magnetic fieldalong the magnetic field lines, whereby an accumulation (separate fromthe roller surface 24) of carrier particles and the toner particlesadhering to them is created pointing outwards on the surface of theroller 24 in the area of the poles of the magnet elements 28, 30, 32,34. Such a separate accumulation of carrier particles is designated as amagnetic brush due to the brush-like shape.

A prepared two-component mixture with a predetermined weight proportionof toner particles is supplied to the first magnetic roller arrangement14, whereby the toner particles are triboelectrically charged. Theweight proportion of the toner is typically in the range of 2% to 8%.The feed of the two-component mixture ensues, for example, via a bucketwheel arrangement. A dosing scraper 22 arranged at a predetermineddistance from the first magnetic roller arrangement 14 generates auniform layer of the two-component mixture 20 on the outer surface ofthe roller 24.

The first magnetic roller arrangement 14 comprises, as noted, the onerotating hollow roller 24 inside which a magnetic roller stator 26 isarranged that comprises the magnet elements 28, 30, 32, 34. Thelongitudinal axes of the magnet elements 28, 30, 32, 34 are aligned in aradial direction, whereby north pole N and south pole S of neighboringmagnet elements 28, 30, 32, 34 respectively follow one another, viewedin the circumferential direction. The magnet elements 28, 30, 32, 34 maybe rod-shaped permanent magnets and extend over the entire roller width.In this embodiment, the separation between each of the permanent magnets28, 30, 32, 34 and the inner surface of the roller 24 is set in therange of 0.2 to 1 mm, whereby a separation in the range of 1.2 mm to 3mm results between each of the permanent magnets 28, 30, 32, 34 and theouter circumferential surface of the roller 24.

A constant toner supply in the two-component mixture 20 is ideallypresent in the area of the magnetic brush 18. The toner particles on thecarrier particles of the magnetic brush 18 apply to the surface of theapplicator roller 12 as a uniform toner layer 36. An electrical fieldgenerated by a potential difference between the surface of theapplicator roller 12 and the roller 24 exerts a force on theelectrically charged toner particles, via which the toner particles areloosened from the carrier particles and applied to the applicator roller12. These electrostatic events are explained in detail later.

The applicator roller 12 is directed to a photoconductor (not shown).Corresponding to the latent charge image of the photoconductor, areas ofthe toner layer 36 are transferred to this over an air gap or in directcontact between the applicator roller 12 and the photoconductor. Theareas 38, 40, 42 of the toner layer 36 not transferred to thephotoconductor form the image negative relative to the latent chargeimage and must be removed from the applicator roller 12. The cleaningensues via a second magnetic roller arrangement 16.

Just like the first magnetic roller arrangement 14, this second magneticroller arrangement 16 has a rotating hollow roller 44 and a magneticroller stator 46 that comprises e.g., rod-shaped magnet elements 48, 50,52 that are implemented as permanent magnets and aligned radially. Therotation direction of the applicator roller 12 is indicated with thearrow P1, the rotation direction of the roller 24 with the arrow P2, andthe rotation direction of the roller 44 with the arrow P3. Thetwo-component mixture is transferred in the area 54 from the surface ofthe roller 24 to the surface of the roller 44 with the aid of themagnetic field of the magnet elements 34 and 48. Given a rotation of theroller 24 in the resulting magnetic field, the ferromagnetic carrierparticles, with the toner particles electrostatically adhering to them,are transported between the south pole S of the permanent magnet 34 andthe north pole N of the permanent magnet 48.

The weight proportion of the toner particles in the two-componentmixture in the area 54 is reduced relative to the prepared two-componentmixture supplied in the area 20, as a result of the toner transfer tothe applicator roller 12. This two-component mixture with reduced tonerproportion is transported to the surface of the roller 44 at the area56.

The magnetic field of the magnet element 50 effective in area 56generates a magnetic brush. In the area 56, the separation betweenroller 44 and applicator roller 12 is relatively small. The magneticbrush in the area 56 comprises the two-component mixture with reducedtoner portion. Due to the potential difference between the surfaces ofthe roller 44 and the applicator roller 12, the toner residues 38, 40,42 are loosened from the surface of the applicator roller 12electrostatically and via abrasion of the magnetic brush on the surfaceof the applicator roller 12 and transported in the direction of theroller 44. The two-component mixture of the magnetic brush 56 contactsthe surface of the applicator roller 12 and additionally abrades thetoner particles from the surface of the applicator roller 12. Furthermagnetic brushes 58, 60 are created on the magnet element 52 of thesecond magnetic roller arrangement 16 as well as on the magnet element30 of the first magnetic roller arrangement 14. After the cleaning ofthe surface of the applicator roller 12 with the aid of the magneticbrush in the area 56, the two-component mixture is transported furtherto the surface of the roller 44 and loosened in the area 62 by theroller 44 of the second magnetic roller arrangement 16, and afterwardsis collected in a catch device (not shown) and supplied again to theelectrophotographic process of the printer or copier in which thearrangement 10 is comprised. In other embodiments, the particle mixturefalls directly into a “mixture sump”, in which the two-component mixtureis prepared again.

An arrangement 64 similar to the arrangement 10 from FIG. 1 is shown inFIG. 2. Identical elements have the same reference characters. Incontrast to the arrangement 10 from FIG. 1, a guide element 66 is usedto transfer the two-component mixture in the area 54. Such a guideelement 66 is, for example, fashioned as a guide sheet. The rotationaxis 68 of the first magnetic roller arrangement 14 is arranged (viewedin the vertical direction) above the rotation axis 70 of the secondmagnetic roller arrangement 16. The guide element 66 is arrangedinclined, such that the two-component mixture can glide or slide fromthe first magnetic roller arrangement 14 to the second magnetic rollerarrangement 16 on a suitable plane. Given larger roller separations, orgiven a horizontal arrangement of the rotation axes 68, 70, instead of aguide element 66, it can be advantageous to also provide a conveyerdevice, for example a transport band or a bucket wheel between the firstmagnetic roller arrangement 14 and the second magnetic rollerarrangement 16.

In FIG. 3, the arrangement 10 shown in FIG. 1 is shown with theelectrical potentials of the roller surfaces set in the operating state.Relative to a ground potential as a reference potential, the surface ofthe applicator roller 12 has a potential difference DC1; relative to theground potential, the outer surface of the roller 24 has a potentialdifference DC2; and relative to the ground potential, the outer surfaceof the roller 44 has a potential difference DC3. In the arrangementshown in FIG. 3, a negative toner system is used. Taking into accountthe polarity sign in a negative toner system, the potential differenceDC1 is to be set smaller than the potential difference DC2, and thepotential difference DC3 is to be set greater than the potentialdifference DC1.

If, in another embodiment, a positive toner system is used in thearrangement shown in FIG. 3, under consideration of the polarity signthe potential difference DC1 is to be set smaller than the potentialdifference DC2, and the potential difference DC3 is to be set smallerthan the potential difference DC1.

In the arrangement according to FIG. 3 with a negative toner system, thepotential differences relative to the reference potential are set toDC1=500 volts, DC2=100 volts, and DC3=700 volts. The potentialdifferences are generated by direct voltage sources 72, 74, 76. However,in other embodiments it is also possible to apply one of thesepotentials DC1, DC2, DC3 to reference potential, and to correspondinglyselect the voltage of the other two direct voltage sources.

Negative voltages are also possible with regard to the ground potential.In other exemplary embodiments, other set potentials DC1, DC2, DC3 ofthe surfaces of the rollers 12, 24, 44 set with regard to the referencepotential are also possible. The potentials to be set primarily dependon the composition of the toner material, on the distances between therollers 12, 24, 44, and on the roller materials. The electrostaticevents that are achieved via the set potentials DC1, DC2, DC3 areprimarily dependent on the potential difference (DC1-DC2) (arising fromthe potentials DC1, DC2, DC3) between the surfaces of the applicatorroller 12 and the magnetic roller arrangement 14, and on the potentialdifference (DC1-DC3) between the surfaces of the applicator roller 12and the magnetic roller arrangement 16, under consideration of thepolarity sign.

With an arrangement shown in FIGS. 1 through 3, it is possible to simplyand cost-effectively produce a nearly wear-free system to apply andclean toner on or from rollers 12. The roller 12 to be cleaned, forexample, an applicator roller or a photoconductor roller, is notmechanically stressed or is only slightly mechanically stressed in thecleaning process. This is primarily achieved by the direct absorption ofthe toner 38, 40, 42 in the two-component mixture. The mechanical stressof the toner is also slight or nonexistent via the direct absorption ofthe toner particles into the two-component mixture. Only a very slightheat development also ensues in the application and/or cleaning. In aprint or copy device with an arrangement according to FIGS. 1 through 3,particle mixtures made up of toner particles and carrier particles withdifferent physical properties (meaning with different toner parameters)can be used, whereby a large working range with regard to theeparameters of the particle mixture is possible. Also, no specialadditives are necessary for the cleaning device, as, for example, arenecessary in cleaning systems with blades, in which additional waxesmust be added to the toner.

In an arrangement shown in FIGS. 1 through 3, not only does the inkingof the applicator roller surface ensue with the aid of a magnetic rollerarrangement 14, but also its cleaning. The electrical potentials DC1,DC2, DC3 explained in the description for FIG. 3 and the potentialdifference resulting from this between the surfaces of the applicatorroller 12 and the roller 44 results in an electrical field between therollers 12, 44 whose force acts on the toner particles in the directionof the roller 44 or in the direction of the two-component mixture on theroller surface. The toner can thereby be removed from the applicatorroller 12 in direct contact with the two-component mixture, or betransferred via an air gap between applicator roller 12 and magneticroller arrangement 16 to the two-component mixture on the surface of themagnetic roller arrangement 16.

In FIG. 4, an arrangement for cleaning an applicator roller 17 with theaid of a magnetic roller system 80 with a rotating hollow roller 81 isshown. This arrangement also comprises a cleaning device with magnetelements 96, 98 and a scraper 82 to clean the outer surface of theroller 81. Toner particles 79 to be removed are located on the surfaceof an applicator roller 78. The magnetic roller system 80 is arranged ata predetermined distance from the applicator roller 78 and has amagnetic roller stator 84 on which the permanent magnets 86 through 100are arranged at equal separation from one another on a circuit aroundthe rotation axis 127 of the magnetic roller system 80. The axis of thepoles N, S of each individual permanent magnet 86 through 100 is alignedradial to the rotation axis 127, meaning the north pole or the southpole of each permanent magnet 86 through 100 is facing to the surface ofthe roller 81 of the magnetic roller system 80.

In the area 102, ferromagnetic carrier particles are supplied to theroller 81 as pure carrier particles or with the aid of a particlemixture made up of carrier particles and toner particles. This feed ofcarrier particles can, for example, ensue from a second roller system(not shown) for toner application; this has already been explained inFIGS. 1 and 2. However, in other exemplary embodiments these carrierparticles can also be supplied to the magnetic roller system 80 from areservoir.

The magnetic fields of the stationary permanent magnets 88, 90, 92, 94form magnetic brushes 104, 106, 108, 110, 112 (from carrier particles)on the surface of the roller 81. The permanent magnet 90 is arranged inthe area with least separation between applicator roller 78 and magneticroller system 80. The magnetic brush 106 formed on the surface of theroller 81 abrades on the surface of the applicator roller 78, wherebytoner particles 79 to be removed are rubbed off. The toner particles 79attach to the carrier particles of the magnetic brush 106. Thedetachment of the toner particles 79 from the surface of the applicatorroller 78 and the attachment of these toner particles to the carrierparticles of the magnetic brush 106 is furthermore influenced by theforce of an electrical field on the carrier particles 79, and by theparticles abrading on the surface of the applicator roller 12. Thiselectrical field is generated due to the potential difference DC betweenthe surfaces of the applicator roller 78 and the roller 81, which isadjusted with the aid of a direct voltage source 116.

The rotation direction of the applicator roller 78 and the roller 81 arethe same, as indicated by the arrows P4 and P5. It is thereby achievedthat a large quantity of ferromagnetic carrier particles on theapplicator roller 112 to be cleaned is directed to the region of themagnetic brush 106 on the applicator roller 78, whereby a mechanicalbrush effect, via which carrier particles are abraded from the surface,is exerted on the surface of the applicator roller 78 with the aid ofthe magnetic brush 106. The circumferential speed of the applicatorroller 78 and of the magnetic roller system 80 are of approximately thesame magnitude.

In other exemplary embodiments, the circumferential speed of themagnetic roller system 80 is smaller or larger than the circumferentialspeed of the applicator roller 78. In further exemplary embodiments, therotation directions of the applicator roller 78 and the magnetic rollersystem 80 are opposite to one another, such that, for example, therotation direction of the magnetic roller system 80 is directed counterto the rotation direction according to the arrow P5. It is therebyachieved that the mechanical stress of the carrier particles and tonerparticles is further reduced in the area of the magnetic brush 106. Inan arrangement with rotation direction set counter to the arrow P5, theelements of the arrangement (meaning the area 102 as well as the scraper82) are to be arranged mirrored on the straight lines through bothrotation axes of the applicator roller 78 and the magnetic roller system80. The further magnetic brushes 104, 108, 110, 112 then in turn form onthe permanent magnets 92, 88, 86, 100 arranged mirrored on thesestraight lines.

The toner particles removed from the applicator roller 78 in the area ofthe magnetic brush 106 are acquired by the carrier particles of thismagnetic brush and transported away in the rotation direction of themagnetic roller system 80. The permanent magnet 96 is arranged justbefore the scraper 82 in the rotation direction P5 of the magneticroller system 80. The blade of the scraper 82 is arranged at apredetermined distance from the surface of the roller 81, whereby a partof the particle mixture made up of carrier particles and toner particlesis stripped from the surface of the magnetic roller system 80 given arotation motion of the magnetic roller system 80.

Due to the force acting on the ferromagnetic carrier particles of theparticle mixture via the magnetic field of the permanent magnet 96, notjust one magnetic brush is held directly on the north pole N of thepermanent magnet 96 on the surface of the roller 81, but rather strippedcarrier particles are additionally held in the area 112 with the aid ofthe scraper 82, such that a cluster made up of carrier particles andtoner particles forms in the area in front of the scraper 82. Thiscluster is also designated as a standing particle mixture. The forceeffect on the carrier particles becomes less with increasing distancefrom the permanent magnet 96, whereby parts of the two-component mixturein the lower area 114 of the cluster fall into a catch reservoir (notshown) for reprocessing of the particle mixture.

Given a rotation motion of the hollow roller 81, the carrier particlesand toner particles are mixed and swirled in the are 112 such that,given a rotation motion of the roller 81, the particle mixture abradeson its surface, whereby toner particles that adhere directly to thesurface of the roller 81 are abraded from this. The movement eventswithin the cluster, meaning in the area 112, are explained in detailfurther below in connection with FIG. 7. In other embodiments, theparticle mixture falls directly into a “mixture sump”, in which thetwo-component mixture is prepared.

FIG. 5 shows primarily the arrangement from FIG. 4 that here, however,serves for the development of a latent charge image that is located onthe surface of a photoconductor drum 77. A toner layer 118 is applied orattached to the surface of the photoconductor drum in the areas to beinked. The assembly of the arrangement shown in FIG. 5 is similar to thearrangement shown in FIG. 4 to clean the applicator roller 78. Identicalelements have the same reference characters.

In area 120, a two-component mixture (meaning a particle mixture made upof carrier particles and toner particles) in which the toner particleshave a weight proportion in the range of 2% to 8% of the particlemixture is supplied to the magnetic roller system. As already specifiedin connection with FIG. 4, a magnetic brush is formed in the area 106 bythe permanent magnet 90. This magnetic brush contacts the surface of thephotoconductor drum 77. As already noted, a latent charge image ispresent on this surface. Due to the charge image in the areas to beinked, the surface of the photoconductor drum 77 has a potentialdifference DC relative to the roller 81 that is generated by a directvoltage source 122.

Given a negative toner system, meaning given negatively charged tonerparticles, the potential of the areas of the photoconductor drum 77 tobe inked is to be set positive relative to the potential of the surfaceof the roller 81. In contrast, given a positive toner system thepotential of the areas of the photoconductor drum 77 to be inked is tobe set negative relative to the potential of the surface of the roller81.

The potential difference between the areas of the photoconductor drum 77to be inked and the roller 81 effects the electrostatic application oftoner particles 118 on the surface of the photoconductor drum 77 in theareas to be inked. In the areas of the photoconductor drum 77 that arenot to be inked (the “background area”), a potential difference oppositerelative to that of the areas to be inked is to be set, whereby a forceeffect is effected on the toner particles in the direction of the roller81, and thus no toner particles are deposited in the background area.The force effects on the toner particles as a result of the potentialdifferences have already been explained in the figure specification withregard to FIG. 3. The scraper-magnet element arrangement shown in FIG. 5for cleaning the magnetic roller surface has already been specified inconnection with FIG. 4.

In FIG. 6, the magnetic roller system 80 that is used in thearrangements shown in FIGS. 4 and 5 is shown enlarged. The distancebetween the blade of the scraper 82 and the outer surface of the roller81 is designated with A1. This distance A1 is set in the range of 0.05to 6 mm, dependent on the physical properties of the particle mixture.In the shown embodiment, the distance A1 is set in the range of 0.1 mmto 4 mm. The longitudinal axis 123 of the permanent magnet 96 arrangedon the magnetic roller stator 84 is arranged at a predetermined distanceA2 (viewed in the rotation direction of the roller 81) in front of theblade of the scraper 82. This separation A1 is set in the range of 0.01to 10 mm, dependent on the physical properties of particle mixture andon the circumferential speed. A particularly effective cleaning effectcould be achieved given a separation in the range of 4 mm to 6 mm.

The longitudinal axes 123, 124, 125, 126 of the permanent magnets 86through 100, shown via dash-dot lines, go through the rotation axis 127,meaning the center points of the north pole N and the south pole S ofthe permanent magnets 86 through 100 line approximately on the straightlines 123 through 126. The straight lines 123 through 126 have anangular separation of 45° from one another, meaning the permanentmagnets 86 through 100 are arranged at the same angular separation fromone another on an orbit around the rotation axis 127. A separation inthe range of 0.2 mm to 1.5 mm is respectively set between the permanentmagnets 86 through 100 and the inner surface of the roller 81. Thedistance between the permanent magnets 86 through 100 and the outersurface of the roller 81 results corresponding to the material strengthof the roller 81, and is in the range of 2.3 mm to 3.5 mm.

What has proven particularly advantageous is a separation in the rangeof 0.2 mm to 1 mm between the side of the permanent magnets 86 through100 facing the roller 81 and the inner surface of the roller 81, and inthe range of 2 mm to 3 mm between the side of the permanent magnets 86through 100 facing the roller 81 and the outer surface of the roller 81.Given these separations, not only are suitable magnetic brushes formed,but rather also a cluster-like accumulation of the particle mixture inthe area 112, as is shown in FIGS. 4 and 5. However, the distancebetween the permanent magnets 86 through 100 and the surface of theroller 81 is dependent on the field strength of the magnet elements 86through 100 used, on the print speed of the print or copy device, mostof all on the circumferential speed of the outer roller surface, on thephysical properties of the toner used, and particularly on the physicalproperties of the carrier particles.

For example, ferrite and iron can be used as carrier particle material,whereby the magnetic saturation of the carrier particle material isparticularly significant. Furthermore, the separation is dependent onthe overall arrangement of the print or copy device. Thus distances thatare outside of the cited ranges can also be set when the circumferentialspeed increases, other toner material is used, other carrier particlematerial(s) is/are used, and/or a changed overall arrangement of theprint or copy device is used.

A section of the magnetic roller system 80 is shown in FIG. 7 togetherwith the scraper 82, whereby the movements within the particle mixture(that result given a rotation motion of the roller 81 in the directionof the arrow P5) are shown with the aid of the arrows P6, P7, P8, P9.The arrangement of the particle mixture in the area 112 is also shown inmore detail relative to the representations of FIGS. 4 and 5. A magneticbrush 128 is formed on the north pole N of the permanent magnet 96 viaits magnetic field. An accumulation of the particle mixture made up oftoner particles and carrier particles (that are held in this area by themagnetic field of the permanent magnet 96) forms cluster-like in frontof the blade of the scraper 82.

As indicated by arrow P6, the particle mixture is transported on theroller surface between the magnetic brushes in the areas 110 and 128 atapproximately the circumferential speed of the roller 81. The particlemixture is conveyed from the magnetic brush in area 128 to thecluster-like accumulation of the particle mixture in front of thescraper 82. As already explained, a part of the particle mixture is heldcluster-like in front of the scraper 82 (viewed in the rotationdirection of the roller 81) by the field forces of the permanent magnets96, 98 in the area 130. Via the rotation motion of the hollow roller 81and via the feed of further particle mixture connected therewith, arotating, roller-shaped movement (that is indicated with the aid of thearrow P8) forms within the particle mixture in front of the scraper 82.

The particle mixture is circulated in the area 130 in front of thescraper 82, whereby it abrades on the surface of the roller 81.Primarily the carrier particles abrade, whereby toner particles thatdirectly adhere to the roller surface are abraded from the rollersurface. The formation of an electrically insulating crust-like layerand electrically insulating areas made up of toner particles on themagnetic roller surface is effectively prevented by the abrasion of thetoner particles on this surface. Electrostatic events such as thetransfer of toner particles from or to the roller 81 are thus notimpaired. Dependent on the field forces of the particle mixtures 96, 98,a more or less large cluster-like accumulation 130 forms in front of thescraper 82. This accumulation 130 is also designated as a standingparticle mixture.

In the lower area of the cluster-like accumulation 130, the forces ofthe magnetic fields of the permanent magnets 96, 98 acting on thecarrier particles are less than at the roller surface, such that parts114 of the particle mixture fall down in the arrow direction of thearrow P9 into a catch reservoir (not shown). The distance A2 (see FIG.6) to be set between the permanent magnet 96 and the blade of thescraper 82 is dependent on the circumferential speed of the roller 81,on the surface roughness of the roller 81, on the toner used, on thecarrier particle material used, on the speed of the print or copydevice, and on the overall arrangement of the print or copy device.

The surface of the roller 81 is electrically conductive. It can, forexample, comprise aluminum, copper, nickel, conductive plastic or acombination of these materials, for example an alloy. In other exemplaryembodiments, the poles N, S of the magnet elements 86 through 100 canvary in shape, design and field strength. The shape of the magnetelements 86 through 100 can thus also not be rod-shaped, such that onlythe pole N, S facing the roller surface acts in the direction of thenormal. The magnet elements 86 through 100 can also have different fieldstrengths. A resulting magnetic field that results via an addition ofthe field vectors of the magnetic fields results between the poles N, Sof permanent magnets 86 through 100 with opposite alignment arrangednext to one another, for example between the south pole S of thepermanent magnet 94 and the north pole N of the permanent magnet 96. Theferromagnetic carrier particles of the two-component mixture align onthe field lines of the resulting magnetic field. The transport of thecontinuously provided two-component mixture to the surface of the roller81 ensues via its rotation.

The roller 81 has a roughness in the range of 1 μm to 5000 μm. It hasproven to be particularly advantageous to set the roughness in the rangeof 10 μm to 3000 μm. Given this roughness, a secure transport of theparticle mixture is ensured and the detachment of toner particles fromthe roller surface is not hindered. The separation A1 between thesurfaces of the scraper 82 and the roller 81 is preferably less than thethickness of the layer of the particle mixture in front of the scraper82. The thickness of the layer of the particle mixture remaining afterthe scraper 82 is limited by the distance A1 between roller surface andscraper blade, and can be set by changing the separation A1.

The part of the particle mixture blocked by the scraper 82 forms thestanding particle mixture relative to the roller 81 on its surface. Theforce with which the ferromagnetic particle mixture made up of tonerparticles and carrier particles adheres to the surface of the roller 81is dependent on the ferromagnetic properties of the carrier particlematerial, on the magnetic field strength of the magnet elements 86through 100, primarily on the field strength of the permanent magnets96, 98, and on the distance between the surface of the roller 81 and therespective permanent magnets 86 through 100.

The standing particle mixture in the area 112 or 130 in front of thescraper 82 abrades on the outer surface of the roller 81 given arotation motion of the roller 81. Via this abrasion, the toner adheringto the surface of the roller 81 is rubbed off and acquired again by theparticle mixture, whereby the abraded toner particles electrostaticallyadhere to the carrier particles. It is thereby achieved that a permanenttoner particle layer on the surface of the roller 81 is prevented, andthe electrostatic process in the printer or copier is not impaired.

The portions of the particle mixture that pass the scraper 82 remain onthe surface of the roller 81. In other exemplary embodiments, these canalso be separated from the roller surface via corresponding designlayout of the magnet stator 136 (see FIG. 8) and be supplied to a catchdevice, for example, the mixture sump of the printer or copier, or betransferred to an adjacent magnetic roller system.

In order to reduce the mechanical energy necessary to implement thecleaning process, it is possible in other embodiments to provide theouter surface of the roller 81 with a coating that has a very lowsurface energy. Such a coating can, for example, be produced with theaid of Teflon. The entire roller 81 can also be produced from such amaterial. However, in order to not negatively influence theelectrostatic process, such a coating should have noelectrically-insulating properties, but rather should be correspondinglyconductive for charge transport from and to the roller 81.

Embodiments are also possible in which the highly-insulating materialwith low surface energy is only applied in the recesses of a roughsurface of the roller 81. The remaining conductive areas ensure thenecessary charge flux. The arrangement for cleaning requires noadditional auxiliary energy. Furthermore, the abrasion eventsadditionally triboelectrically charge the toner in the cleaning.

The arrangement for cleaning of the surface of magnetic roller systemscomprise no wearing parts. Via the simple design, a compactimplementation of the cleaning device and the entire print or copydevice is also possible. It is also suitable to use various particlemixtures with different toner parameters. The magnetic roller system 80can both remove toner particles from applicator roller 78 and fromphotoconductors and develop latent charge images on photoconductors andink applicator rollers 78. In place of an applicator roller 78, in otherexemplary embodiments, applicator bands or transfer bands can be used.In further exemplary embodiments, other magnet elements such aselectromagnets are used in place of the permanent magnets. Thearrangements shown in FIGS. 4 and 5 can, for example, also be used in anarrangement according to FIGS. 1 and 2.

An arrangement for cleaning the surface of an applicator roller 132 isshown in FIG. 8. This arrangement serves to remove a toner layer 133 andtoner residues from the surface of the applicator roller 132, andcomprises a magnetic roller arrangement 134 with a magnetic rollerstator 136 which has permanent magnets 138, 140, 142, 144, and with arotating hollow roller 162 that is driven in the rotation direction P11with an actuation unit (not shown).

The toner particles of the toner layer 133 electrostatically adhere tothe surface of the applicator roller 132. A drive unit (not shown)drives the applicator roller 132 in the rotation direction of the arrowP10. A direct voltage source 160 generates a potential difference DCbetween the surfaces of the applicator roller 132 and the roller 162.The force of the electrical field generated by the potential differenceDC on the toner particles of the toner layer 133 is directed towards thesurface of the roller 162.

In the area 146, ferromagnetic carrier particles are supplied to themagnetic roller system 134 with the aid of a device (not shown). Inother exemplary embodiments, in the area 146 a particle mixture made upof electrically charged toner particles and ferromagnetic carrierparticles can be supplied to the magnetic roller system 134.

The alignment of the poles N, S of the magnet element 138 is, just likethe alignment of the poles of the magnet elements 140, 142, 144, radialto the rotation axis 164, meaning that the north pole N or the southpole S of a magnet element 138, 140, 142, 144 is respectively facing theinner surface of the roller 162. The magnet element 140 is arranged inthe area with the lowest separation between the applicator roller 132and the roller 162. If the poles N, S are considered as points, thepoles N, S of the magnet element 140 lie approximately on a straightline 166 (represented as a dash-dot line) that intersects the rotationaxes 164, 165 of the magnetic roller system 134 and the applicatorroller 132.

The longitudinal axis of the magnet element 138 that intersects therotation axis 164 is skewed relative to the straight line 166 byapproximately 50° counter to the rotation direction P11 of the roller162. The longitudinal axis of the magnet element 142 is skewed relativeto the straight line 166 by approximately 100° in the rotation directionP11 of the roller 162. The longitudinal axes of the magnet elements 142and 144 also run through the rotation axis 164 of the magnetic rollersystem 134.

Magnetic brushes form on the outer surface of the roller 162 due to themagnetic fields of the magnet elements 138 through 144. The separationbetween the outer surfaces of the roller 162 and the applicator roller132 is set such that the magnetic brush formed by the magnetic field ofthe magnet element 140 in the area 150 contacts the roller surface ofthe applicator roller 132. The toner particles of the layer 133 areremoved from the surface of the applicator roller 132 and adhere to theferromagnetic carrier particles of the magnetic brush 150. As alreadyspecified, this event is supported by the potential difference DCgenerated between the surfaces of the applicator roller 132 and theroller 162 of the magnetic roller system 134 by the direct voltagesource 160. The potential difference DC to be set is, as alreadyspecified in connection with FIG. 7, dependent on the toner system used.

The transport of the carrier particles between the magnet elements 138and 140 ensues on the surface of the roller 162. The particle mixturemade up of ferromagnetic carrier particles and the toner particlesremoved from the surface of the applicator roller 132 is transportedbetween the magnet element 140 and the magnet element 142 via therotation motion of the roller 162 in the direction of the arrow P11.

The magnetic fields of the magnet elements 142, 144 act in primarily thesame direction, whereby the north poles N of the magnet elements 142,144 are directed towards the surface of the roller 162. The adjacentpoles N, N of the two magnet elements 142, 144 facing the particlemixture are thereby similar. The adjacent edges of these magnet elements142, 144 are (viewed in the rotation direction) arranged at a separationin the range of 0.01 to 10 mm from one another, whereby the distancebetween the adjacent edges does not have to be constant.

The magnetic fields of the magnet elements 142, 144 overlap, whereby theresulting magnetic field at each point of the space of the resultingvector is an addition of the field vectors generated by the magnetelements 142, 144. In the area between the magnet elements 142, 144 onthe surface of the roller 162, the field vectors have approximately thesame magnitude and are directed approximately opposite, such that theresulting magnetic field strength in this area is low. The field vectorshave the same magnitude at a distance absorption approximately 5 mm fromthe surface of the roller 162, however the directions are no longerapproximately opposed. At a distance between 5 mm and 15 mm from thesurface of the roller 162, on an axis of symmetry between the axes ofthe poles N, S of the magnet elements 142, 144, an area with highmagnetic field strength and high magnetic flux density exists that isalso designated as a magnetic far field.

The ferromagnetic carrier particles are pulled in the direction of highmagnetic field strengths. This means that the carrier particles arepulled corresponding to the resulting magnetic field strength into thearea 156 with high magnetic field strength at a distance between 5 mmand 15 mm from the surface of the roller 162. Given a rotation motion ofthe roller 162, carrier particles are conveyed into the area 152, thenpushed into the area 156 and, in the further course, supplied to themagnetic brush in area 154, whereby in area 156 they have a separationfrom the surface of the roller 162 as a result of the resulting magneticfield.

The particle mixture made up of carrier particles and toner particles inthe area 158 falls down from the magnetic brush 154 into a catchreservoir (not shown) (for example, into the “mixture sump” of theprinter or copier) for reprocessing of the particle mixture. During theentire cleaning event, toner particles adhere to the carrier particles.The toner particles abraded from the roller surface likewise adhere tothe carrier particles and are transported together with these.

A self-cleaning effect of the conductive surface of the roller 162 isachieved in the arrangement shown in FIG. 8 via the arrangement of themagnet elements 138 through 144. This self-cleaning effect is based onthat, given the two adjacent magnet elements 142, 144, the north andsouth poles N, S are aligned in approximately the same direction,whereby a standing particle mixture is respectively generated on thesurface of the roller 162 in the areas 152, 154 that abrades on thesurface and loosens toner particles from it.

The resulting magnetic field has a low resulting field strength betweenthe magnet elements 142, 144 on the surface of the roller 162. Given therotation of the roller 162, the transport of the particle mixture ensuesin the area 156 at a separation from the surface of the roller 162. Theparticle mixture hardens in the area of the magnetic brush 152, wherebythe mixture transport is inhibited. The force with which the particlemixture made up of ferromagnetic carrier particles and electricallycharged carrier particles adheres to the surface of the roller 162 isdirectly dependent on the magnetic field strength of the magnet elementsof the magnetic roller stator 136, primarily on that of the magnetelement 142.

In the areas 152, 154, the standing particle mixture adhering to thesurface of the roller 162 rubs against the toner particles adhering tothe surface of the roller 162. The abraded toner particles adhere to thecarrier particles and fall down into area 158 with these. The thuslycleaned surface of the roller 162 ensures that the continuouselectrostatic process in the printer or copier is not impaired.Furthermore, due to the friction between carrier particles and tonerparticles, a triboelectrical charge ensues of the toner particlespartially charged by the preceding electrophotographic process.

In the magnetic far field, the north poles N of the magnet elements 142,144 can be considered as a common north pole. The particle mixture ispulled in the direction of the far field, from the surface of the roller162 into the area with high magnetic field strength that is, however,less than the field strength on the roller surface at the poles. Theparticle mixture thereby hardens on the roller surface in the areas atthe poles N, N of the magnet elements 142, 144 and forms accumulationsthere. In these accumulations, a part of the particle mixture is pushedaway from the roller surface by the conveyed particle mixture. Themagnetic field strength decreases with the distance from the magnetelement. The particle mixture is then pushed along by the conveyedparticle mixture. The design of the magnetic roller stator 136 and thearrangement of the magnet elements 138 through 144 act on this stator136, so that in area 158, the resulting magnetic field on the surface ofthe roller 162 is formed such that the particle mixture falls down.

In other embodiments, arrangements of the magnet elements are providedthat enable a further transport on the roller 162 or a transfer of theparticle mixture to an adjacent magnetic roller system. The separationarising of the particle mixture from the surface of the roller 162 inthe area 156 is primarily dependent on the magnetic field strength ofthe magnet elements 142, 144, the separation of the north poles N ofthese magnet elements 142, 144 and the outer surface of the roller 162,the thickness and the material of the roller 162, the roughness of theroller 162, and the circumferential speed of the roller 162.

The falling off of the particle mixture in the area 158 ensues when thecentrifugal force (that is caused by the rotation of the roller 162)tangential to the roller 162 prevails relative to the radially actingmagnetic force on the particle mixture. A transfer to an adjacentmagnetic roller system ensues when a sufficiently great magnetic flux iscreated by the magnet configuration between the adjacent roller systemand the magnetic roller system 134.

Given a rotation motion of the rollers 132, 162, the standing particlemixture at the north poles N (acting approximately in the samedirection) of the magnet elements 142, 144 is replaced by newly suppliedparticle mixture, and thus continuously exchanged. A continuousenrichment of the of the standing particle mixture with toner does notensue. To reduce the necessary mechanical energy acting on the particlemixture during the cleaning process, the roller 162 can be provided witha coating that has a very low surface energy, for example with Teflon.However, no sealed coating should be used that is electricallyinsulating in order to prevent the electrostatic process. For chargetransport from and to the roller 162, its surface must be electricallyconductive.

In alternative embodiments, highly insulating materials with low surfaceenergy can also be introduced into the recesses of a rough surfacestructure of the roller 162. The remaining conductive areas of theroller 162 then ensure the necessary charge flow. In the arrangementshown in FIG. 8, no additional devices are necessary to remove tonerresidues on the roller 162. A very compact assembly of the overallsystem is thus possible. Additional auxiliary energy to clean the roller162 is unnecessary. The arrangement does not need wearing parts orconsumable materials. It is thereby low-maintenance.

This arrangement can be used for various toner types that have differenttoner parameters. In another embodiment, the arrangement shown in FIG. 8for cleaning a magnetic roller 162 is used that serves to ink a surface.Incorrectly charged toner particles can be comprised in the particlemixture for inking. Due to the force acting on these toner particles viaa potential difference, these toner particles are not transported to thesurface to be inked, but rather adhere via this force to the surface ofthe magnetic roller 162 on which they then form an electricallyinsulating layer. The formation of such a layer is prevented by theinventive cleaning of this magnetic roller 162.

An arrangement to ink a latent charge image arranged on a photoconductordrum 168 in an electrophotographic printer or copier is shown in FIG. 9.The arrangement is substantially designed as the arrangement shown inFIG. 8 for cleaning the applicator roller 132. Identical elements havethe same reference characters. The photoconductor drum 168 is moved inthe direction of the arrow P10 and is arranged at a distance from amagnetic roller system 134. The assembly of the magnetic roller system134 was already specified in connection with FIG. 8.

In the arrangement shown in FIG. 9, in the area 172, a two-componentmixture (meaning a particle mixture made up of toner particles andcarrier particles) is supplied that has a high weight proportion oftoner particles, in the range of 2% to 8%. In the area 150, the magneticfield of the magnet element 140 forms a magnetic brush (made up of thetwo-component mixture) that contacts the surface of the photoconductordrum 168. A latent charge image is located on this surface of thephotoconductor drum 168, in that the areas to be inked with toner have ahigh potential difference DC relative to the surface of the roller 162.Via this potential difference DC, the toner particles are detached fromthe surface of the roller 162 and attached to the surface of thephotoconductor drum 168.

A part of the toner particles of the two-component mixture that issupplied to the arrangement in area 172 is directly applied to thesurface of the roller 162 and forms a toner layer on the surface of theroller 162. Toner particles are also applied to the surface of theroller 162 via the force effects (already specified) of electricalfields on the toner particles, for example in the background area andgiven incorrectly charged toner particles. Via roller-shaped rotatingmotions within the particle mixture, the standing particle mixture inthe areas 152, 154 rubs against the surface of the roller 162. The tonerparticles on the surface are rubbed off, as already specified inconnection FIG. 8. The formation of the standing particle mixture, thetransport and the falling off of the particle mixture in the area 158likewise ensues as in the arrangement shown in FIG. 8. Given thearrangement shown in FIG. 9, in particular possible are such embodimentsthat have already been specified in connection with FIG. 8. The “memoryeffect” is effectively prevented via the cleaning of the roller 162 inan electrophotographic printer or copier with an arrangement accordingto FIG. 9.

In FIG. 10, the magnetic roller system 134 according to FIGS. 8 and 9 isshown in an enlarged representation. The angles encompassed between theaxes 174 through 177 of the poles N, S of the magnet elements 138through 144 are specified. The axes 174 through 177 of the magnetelements 138 through 144 respectively have an angular separation ofapproximately 5° from one another. The magnetic field strength of themagnet elements 142, 144, the overall size of the magnet elements 142,144, and the absolute separation between the two magnet elements 142,144 are to be considered in the setting of the angular separationbetween the axes 176, 177 of the poles N, S of the identically alignedmagnet elements 142, 144. In other embodiments, the angle to be set canalso accordingly have a value deviating significantly from 50°: forexample, this angle can be in the range between 10° and 100°.

A section of the magnetic roller system 134 is shown in FIG. 11 togetherwith the particle mixture made up of toner particles and carrierparticles given a rotation motion of the roller 162. The motions of theparticle mixture are recognizable using the arrows P12 through P16. Theparticle mixture is transported from the south pole S of the magnetelement 140 to the north pole N of the magnet element 142 in the arrowdirection of the arrow P12 on the surface of the roller 162 via itsrotation motion. As already specified, the north poles N of the magnetelements 142, 144 pointing in approximately the same direction lead tothe stationary particle mixture in the area of the north pole N of themagnet element 142 on the surface of the roller 162.

As a result of the amount of the particle mixture conveyed in the arrowdirection P12 on the surface of the roller 162, and via its rotationmotion, a rotating, roller-shaped motion and a roller-shaped swirlingand mixing is created within the standing particle mixture on thesurface of the roller 162 in the area 152. The motion of the particlemixture in the area 152 is visible via the arrow P13. The parts of thestanding particle mixture (that, in the magnetic far field in the outerarea 152 of the magnetic brush, are pushed away by the increasingaccumulation of the particle mixture and that, as already specified, arepulled in the direction of the arrow P14 into the mutual magnetic farfield of the magnet elements 142, 144) have in area 156 a separationfrom the surface of the roller 162, whereby the particle mixture istransported through the area 156 towards the area 154 by the continuousconveyance in the area 152 in the direction of the arrow P14.

Corresponding to the arrow P15, a part of the particle mixture issupplied to the area 154 in front of the north pole N of the magnetelement 144 at a distance from the surface of the roller 162 in the area156. The remaining part falls directly into a catch reservoir (notshown), for example into a mixture sump of the printer or copier. Themagnetic field of the magnet element 144 also generates a standingparticle mixture on the surface of the roller 162 in the area 154,whereby a rotating, roller-shaped motion also ensues there in theparticle mixture, via which toner particles are abraded from the surfaceof the roller 162. This rotating motion within the standing particlemixture is represented by the arrow P16.

The continuous feed of the particle mixture in the area 154 effects anaccumulation of particles in this area 154. Particles in areas with lowmagnetic field strength are hereby pushed outwards, meaning away fromthe roller surface. The force effect of the magnetic field decreaseswith increasing distance from the magnet element 144, and a part of theparticle mixture in the outer area 154 of the magnetic brush falls downas a result of gravity. The particle mixture falling down is shown inarea 158.

In an alternative exemplary embodiment, the north and south poles N, Sof the magnet elements 142, 144 are arranged opposite to the alignmentshown in FIG. 11, meaning the south poles S of the magnet elements 142,144 act in approximately the same direction and are facing the surfaceof the roller 162. The arrangements according to FIGS. 1 through 11 aresectional representations of roller arrangements. The magnet elementsshown therein are preferably arranged on the total width of therespective magnetic roller. The width of the magnetic roller is therebypreferably larger than or equal to the possible print width of theprinter or copier.

The magnet elements can also be comprised of a plurality of individualmagnets. The axis through the poles N, S of the magnet elements isdesignated in the figure specifications as the longitudinal axis of themagnet elements. Via the design layout, in further embodiments, theopposite poles N, S of the poles N, S facing the particle mixture do notact in the opposite direction. The shape of the raised accumulations ofthe particle mixture, meaning of the magnetic brushes and the standingparticle mixture, are influenced by this design layout. In thisexemplary embodiment, the poles N, N act approximately in the radialdirection.

In FIG. 12, the field distribution in the magnetic near field directlyon the surface of the roller 162 of the magnetic roller system 134 isshown in a polar coordinate system. The magnetic flux density is plottedon the axis of the polar coordinate system. Given a multiplication by2000, the specified number values of 0 to 1 specify the magnetic fluxdensity in Gauss. Given a multiplication by 0.2, these number valuesspecify the magnetic flux density in Tesla. The longitudinal axisthrough the magnet element 140 is the 90° axis in the diagram.

The alignment of the resulting magnetic field that generates themagnetic flux density is characterized by the letters N and S arrangednear the curves in the diagram. The flux density is directlyproportional to the magnetic field strength, whereby the magnetic fluxdensity is the product of the absolute permeability and magnetic fieldstrength. In the area 152, the magnet element 142 shown in FIG. 11generates a maximum magnetic flux density of 1800 Gauss on the surfaceof the roller 162. The magnet element 144 likewise shown in FIG. 11generates a maximum flux density of approximately 1780 Gauss on thesurface of the roller 162. A minimum resulting flux density ofapproximately 100 Gauss results in the area 156.

The field distribution in the magnetic far field is shown in FIG. 13 ata distance of approximately 9 mm from the surface of roller 162. Thescale gradation coincides with the scale gradation of the diagram shownin FIG. 12. In the diagram shown in FIG. 13, the magnetic far field inthe area 156 between the magnet elements 142, 144 at a distance ofapproximately 9 mm from the surface of the roller 162 has a relativelyhigh magnetic flux density of up to 950 Gauss. The maximum difference ofthe magnetic flux density in the area 156 between the surface and anarea at a distance of 9 mm from the surface amounts to 850 Gauss. Thus,at a distance of 9 mm in the area 156, the magnetic field is stronger bya multiple than at the surface of the roller 162. Due to the strongmagnetic far field, the detachment of the particle mixture from thesurface of the roller 162 ensues as specified in the area 156 and thestanding particle mixtures in the areas 152, 154.

Additionally, the arrangement specified in FIGS. 8 and 9 can be providedin other exemplary embodiments with a scraper that, for example, isarranged at a predetermined distance (viewed in the rotation directionof the roller 162) after the magnet element 144. Thus, in furtherembodiments, the arrangements shown in FIGS. 8 and 9 can be combinedwith elements of the arrangements shown in FIGS. 4 and 5. All magnetelements can be implemented depending on the requirements for the fieldstrength and on the embodiment as a electromagnets or as permanentmagnets. The arrangements shown in FIGS. 4 and 5 or 8 and 9 for theapplication of toner and to clean surfaces can also be used inarrangements that are designed like the arrangements shown in FIGS. 1and 2.

In all embodiments, it is possible to overlap the potential differencesDC generated by the direct voltage sources with potential differencesgenerated by alternating voltage sources. If a plurality of directvoltage sources are provided in an embodiment, potential differencesgenerated even individually by these direct voltage sources can also beoverlapped with potential difference generated by one or by manyalternating voltage sources. The potential difference generated by thealternating voltage source effects a motion and thereby a loosening ofthe toner particle accumulation in the two-component mixture.

Although preferred exemplary embodiments are shown and details in thedrawings and in the preceding specification, these should be viewed aspurely exemplary and not as limiting the application. It is to be notedthat only the preferred exemplary embodiments are shown and described,and all changes and modifications that lie within the scope ofprotection of the invention in the present and future should beprotected.

Embodiments of the present invention may be described in terms offunctional block components and various processing steps. Suchfunctional blocks may be realized by any number of hardware componentsconfigured to perform the specified functions. For the sake of brevity,conventional aspects and elements may not be described in detail.Furthermore, the connecting lines, or connectors shown in the variousfigures presented are intended to represent exemplary functionalrelationships and/or physical or logical couplings between the variouselements. It should be noted that many alternative or additionalfunctional relationships, physical connections or logical connectionsmay be present in a practical device. Moreover, no item or component isessential to the practice of the invention unless the element isspecifically described as “essential” or “critical”.

Reference List

-   10 roller arrangement-   12 applicator roller; first carrier element-   13 photoconductor element; second carrier element-   14 first magnetic roller arrangement; toner application unit-   16 second magnetic roller arrangement; cleaning unit-   18 magnetic brush-   20 prepared two-component mixture-   22 dosing scraper-   24 rotating hollow roller-   26 magnetic roller stator-   28, 30, 32, 34 permanent magnet-   36 toner layer-   38, 40, 42 toner residues-   44 rotating hollow roller-   46 magnetic roller stator-   48, 50, 52 permanent magnets-   54 area of the transfer of the particle mixture-   56, 58, 60 area with magnetic brush-   62 particle mixture falling down-   64 roller arrangement-   66 guide element-   68, 70 rotation axis-   72, 74, 76 direct voltage sources-   77 photoconductor drum-   78 applicator roller-   79 toner layer-   80 magnetic roller system-   81 rotating hollow roller-   82 scraper-   84 magnetic roller stator-   86, 88, 90, 92, 94, 96, 98, 100 permanent magnet-   102 supplied particle mixture-   104, 106, 108, 110 area with magnetic brush-   112 standing particle mixture-   114 falling particle mixture-   116 direct voltage source-   118 toner particle layer-   120 supplied particle mixture-   122 direct voltage source-   123, 124, 125, 126 normal through poles-   127 rotation axis-   128 area with magnetic brush-   130 standing particle mixture-   132 applicator roller-   133 toner layer-   134 magnetic roller system-   136 magnetic roller stator-   138, 140, 142, 144 magnet element-   146 supplied carrier particles-   148, 150, 152, 154 area with magnetic brush-   156 area with particle mixture raised from the roller surface-   158 shed particle mixture-   160 direct voltage source-   162 rotating hollow roller-   164, 165 rotation axis-   166 normal through poles-   168 photoconductor drum-   169 inked area of the latent charge image-   170 direct voltage source-   172 area for feeding of the particle mixture-   174, 175, 176, longitudinal axis of the magnet element 177-   P1 through P16 direction arrows P16

1. An electrophotographic print or copy device, comprising: a first carrier element; a toner application unit that transfers toner particles onto the first carrier element aided by a particle mixture made up of electrically charged toner particles and ferromagnetic carrier particles; a second carrier element to which at least one part of the toner particles of the particle mixture are transferred; a cleaning unit for accepting the particle mixture after the transfer of at least one part of the toner particles to the second carrier element, the cleaning unit accepting, with the aid of the supplied particle mixture, the toner particles present on the first carrier element; and a guide element arranged between toner application unit and cleaning unit that is utilized in the transfer of the particle mixture from the toner application unit to the cleaning unit.
 2. The electrophotographic print or copy device according to claim 1: wherein a magnetic field of at least one magnet element is utilized for transfer of the particle mixture from the toner application unit to the cleaning unit.
 3. An electrophotographic print or copy device, comprising: a first carrier element having an outer surface; a toner application unit configured to apply electrically charged toner particles to the surface of the first carrier element; a second carrier element to which at least one part of the toner particles is transferred from the first carrier element; a cleaning unit configured to remove, from the first carrier element, the toner particles remaining on the first carrier element after the transfer, the cleaning unit comprising: a roller that is arranged at a distance from the first carrier element, the roller having a surface upon which is conveyed a particle mixture that comprises electrically charged toner particles and ferromagnetic carrier particles; at least one magnet element arranged stationary inside the roller; a scraper arranged at a distance from the roller surface; the at least one magnet element being arranged in proximity to the scraper such that the carrier particles form at least one raised accumulation on the surface of the roller, and are configured to abrade, given a rotation motion of the roller, on its surface; and a guide element arranged between toner application unit and cleaning unit that is utilized in the transfer of the particle mixture from the toner application unit to the cleaning unit.
 4. The device according to claim 3, wherein the at least one raised accumulation, via forces acting on the carrier particles via the resulting magnetic field of the two magnet elements detach at least a part of the carrier particles from the roller surface in a sub-area between the magnet elements, and that, given a rotation motion of the roller, the particles of the particle mixture in the area of the magnet elements are moved such that they abrade on the surface of the roller.
 5. The device according to claim 4, wherein at least one part of the toner particles that are electrostatically attached to an outer circumferential surface of the roller are rubbed off of this via the motion of the particle mixture.
 6. The device according to claim 3, further comprising further magnet elements whose poles are respectively aligned radially relative to the roller are arranged inside the roller.
 7. The device according to claim 3, further comprising a scraper that is arranged at a distance in the range of 0.1 to 0.4 mm from the roller surface.
 8. The device according to claim 7, wherein, when viewed in a rotation direction of the roller, the first and second magnet element are arranged in front of the scraper in proximity to it.
 9. The device according to claim 7, wherein the scraper is arranged in a lower roller half.
 10. The device according to claim 3, wherein the outer circumferential surface of the roller has a roughness in the range of 1 to 5000 μm.
 11. The device according to claim 3, wherein the roller surface comprises at least one of aluminum, chromium, nickel, copper, conductive plastic and a plastic with a conductive layer.
 12. The device according to claim 3, wherein the surface of the roller is a flame-spraying-method-formed surface.
 13. The device according to claim 3, wherein the magnet elements are permanent magnets.
 14. The device according to claim 3, further comprising: a scraper arranged proximate to the magnetic element in a manner such that the carrier particles form a raised accumulation on the surface of the roller, a rotation motion of the roller causing the carrier particles abrade on its surface.
 15. The device according to claim 14, wherein: when viewed in the rotation direction of the roller, the magnet element is arranged in front of the scraper in its proximity; and the scraper is configured to strip off at least one part of the particle mixture located on the roller surface.
 16. The device according to claim 15, wherein a magnetic field of the magnet element holds, in the area of the scraper, parts of the particle mixture stripped by the scraper, and wherein movements in the particle mixture in an area of the scraper are generated via the rotation motion of the roller and via the scraper positioned such that it is fixed.
 17. The device according to claim 16, wherein at least one part of the toner particles that adhere to the outer surface of the roller are detached from this via motions in the particle mixture.
 18. The device according to claim 14, wherein an axis of poles of the magnet element is aligned radially relative to a rotation axis of the roller.
 19. The device according to claim 14, further comprising: a plurality of magnet elements that are arranged inside the roller, and axes of the poles of the magnets are respectively aligned radially relative to the roller, the poles of adjacent magnet elements having opposite effective directions.
 20. The device according to claim 14, wherein the scraper is arranged in the lower roller half.
 21. The device according to claim 14, wherein the outer circumferential surface of the roller has a roughness in a range of 1 to 5000 μm.
 22. The device according to claim 14, wherein the roller surface comprises at least one of aluminum, chromium, nickel, copper, conductive plastic and a plastic with a conductive layer.
 23. The device according to claim 14, wherein the surface of the roller is a flame-spraying-method-formed surface.
 24. The device according to claim 14, wherein the at least one magnet element is a permanent magnet.
 25. The device according to claim 14, wherein a distance in the range of 0.1 to 0.4 mm is set between the scraper and the roller surface.
 26. The device according to claim 3, wherein at least one of the first and the second carrier element is a roller or a band.
 27. The device according to claim 3, wherein the first carrier element is a photoconductor and the second carrier element is a carrier material to be printed or a transfer element.
 28. The device according to claim 3, wherein the cleaning unit comprises a roller whose rotation direction is the same as the rotation direction of the first carrier element.
 29. The device according to claim 28, further comprising a magnet element arranged stationary inside the roller at a location with a minimal distance between the first carrier element and roller, the axis of the poles of the magnet element running radially relative to the roller.
 30. The device according to claim 29, further comprising a plurality of magnet elements arranged inside the roller, an axis of the poles of each magnet element being aligned radially relative to the rotation axis.
 31. The device according to claim 29, wherein the magnet element is a permanent magnet.
 32. The device according to claim 3, wherein an amount of the ferromagnetic carrier particles conveyed on the roller surface of the cleaning unit comprises a predetermined proportion of toner particles.
 33. The device according to claim 3, wherein the guide element is a guide sheet.
 34. The electrophotographic print or copy device as claimed in claim 3, wherein a magnetic field of the at least one magnet element is utilized for transfer of the particle mixture from the toner application unit to the cleaning unit.
 35. The electrophotographic print or copy device as claimed in claim 3: wherein the first carrier element is an applicator element and the second carrier element is a photoconductor.
 36. An electrophotographic print or copy device, comprising: a first carrier element having an outer surface; a toner application unit configured to apply electrically charged toner particles to the surface of the first carrier element; a second carrier element to which at least one part of the toner particles is transferred from the first carrier element; a cleaning unit configured to remove, from the first carrier element, the toner particles remaining on the first carrier element after the transfer, the cleaning unit comprising: a roller that is arranged at a distance from the first carrier element, the roller having a surface upon which is conveyed a particle mixture that comprises electrically charged toner particles and ferromagnetic carrier particles; at least two magnet elements arranged stationary inside the roller; a scraper arranged at a distance from the roller surface; and a guide element arranged between toner application unit and cleaning unit that is utilized in the transfer of the particle mixture from the toner application unit to the cleaning unit; wherein adjacent poles of both magnet elements facing the particle mixture are uniform and are arranged (viewed in a rotation direction of the roller) at a distance from one another such that the carrier particles on the surface of the roller form, at the magnet elements, at least one raised accumulation whose carrier particles abrade on the surface of the roller given a rotation motion of the roller; and wherein a magnetic field of the at least one magnet element is utilized for transfer of the particle mixture from the toner application unit to the cleaning unit.
 37. An electrophotographic print or copy device, comprising: a first carrier element having an outer surface; a toner application unit configured to apply electrically charged toner particles to the surface of the first carrier element; a second carrier element to which at least one part of the toner particles is transferred from the first carrier element; a cleaning unit configured to remove, from the first carrier element, the toner particles remaining on the first carrier element after the transfer, the cleaning unit comprising: a roller that is arranged at a distance from the first carrier element, the roller having a surface upon which is conveyed a particle mixture that comprises electrically charged toner particles and ferromagnetic carrier particles; at least two magnet elements arranged stationary inside the roller; a scraper arranged at a distance from the roller surface; wherein adjacent poles of both magnet elements facing the particle mixture are uniform and are arranged (viewed in a rotation direction of the roller) at a distance from one another such that the carrier particles on the surface of the roller form, at the magnet elements, at least one raised accumulation whose carrier particles abrade on the surface of the roller given a rotation motion of the roller; the device further comprising: a guide element arranged between toner application unit and cleaning unit that is utilized in the transfer of the particle mixture from the toner application unit to the cleaning unit.
 38. A method to operate an electrophotographic print or copy device, comprising: applying electrically charged toner particles to a surface of a first carrier element aided by a toner application unit; transferring at least one part of the toner particles from the first carrier element to a second carrier element; removing, aided by a cleaning unit, the toner particles remaining on the first carrier element after the transfer from the first carrier element, the cleaning unit comprising a roller that is arranged at a distance from the first carrier element, with at least two magnet elements arranged stationary inside the roller; conveying a particle mixture that comprises electrically charged toner particles and ferromagnetic carrier particles on a surface of the roller; forming at least one raised accumulation of the carrier particles on the surface of the roller at the magnet elements, adjacent poles of both magnet elements facing the particle mixture being uniform and being arranged (viewed in the rotation direction of the roller) at a distance from one another to create the at least one raised accumulation, rotating the roller; abrading, with the carrier particles, on the surface of the roller given the rotation of the roller; and providing a guide element arranged between toner application unit and cleaning unit that is utilized in the transfer of the particle mixture from the toner application unit to the cleaning unit; wherein the first carrier element is an applicator element and the second carrier element is a photoconductor.
 39. A method to operate an electrophotographic print or copy device, comprising: applying electrically charged toner particles to a surface of a first carrier element aided by a toner application unit; transferring at least one part of the toner particles from the first carrier element to a second carrier element; removing, aided by a cleaning unit, the toner particles remaining on the first carrier element after the transfer from the first carrier element, the cleaning unit comprising a roller that is arranged at a distance from the first carrier element, with at least two magnet elements arranged stationary inside the roller; conveying a particle mixture that comprises electrically charged toner particles and ferromagnetic carrier particles on a surface of the roller; forming at least one raised accumulation of the carrier particles on the surface of the roller at the magnet elements, adjacent poles of both magnet elements facing the particle mixture being uniform and being arranged (viewed in the rotation direction of the roller) at a distance from one another to create the at least one raised accumulation, rotating the roller; abrading, with the carrier particles, on the surface of the roller given the rotation of the roller; and providing a guide element arranged between toner application unit and cleaning unit that is utilized in the transfer of the particle mixture from the toner application unit to the cleaning unit; wherein a magnetic field of the at least one magnet element is utilized for transfer of the particle mixture from the toner application unit to the cleaning unit.
 40. A method to operate an electrophotographic print or copy device, comprising: applying electrically charged toner particles to a surface of a first carrier element aided by a toner application unit; transferring at least one part of the toner particles from the first carrier element to a second carrier element; removing, aided by a cleaning unit, the toner particles remaining on the first carrier element after the transfer from the first carrier element, the cleaning unit comprising a roller that is arranged at a distance from the first carrier element, with at least two magnet elements arranged stationary inside the roller; conveying a particle mixture that comprises electrically charged toner particles and ferromagnetic carrier particles on a surface of the roller; forming at least one raised accumulation of the carrier particles on the surface of the roller at the magnet elements, adjacent poles of both magnet elements facing the particle mixture being uniform and being arranged (viewed in the rotation direction of the roller) at a distance from one another to create the at least one raised accumulation, rotating the roller; abrading, with the carrier particles, on the surface of the roller given the rotation of the roller; and providing a guide element arranged between toner application unit and cleaning unit that is utilized in the transfer of the particle mixture from the toner application unit to the cleaning unit.
 41. The method according to claim 40, further comprising: absorbing the toner particles present on the first carrier element with the aid of the cleaning unit.
 42. An electrophotographic print or copy device, comprising: a first carrier element; a toner application unit that transfers toner particles onto the first carrier element aided by a particle mixture made up of electrically charged toner particles and ferromagnetic carrier particles; a second carrier element to which at least one part of the toner particles of the particle mixture are transferred; and a cleaning unit for accepting the particle mixture after the transfer of at least one part of the toner particles to the second carrier element, the cleaning unit accepting, with the aid of the supplied particle mixture, the toner particles present on the first carrier element; and at least one of a first voltage source configured to provide a first potential difference between the toner application unit and the first carrier element, and a second voltage source configured to provide a second potential difference between the cleaning unit and the first carrier element; wherein the electrostatically charged toner particles are electrically negatively charged, that the potential of the first carrier element is positive relative to the potential of the toner application unit, and negative relative to the potential of the cleaning unit.
 43. An electrophotographic print or copy device, comprising: a first carrier element; a toner application unit that transfers toner particles onto the first carrier element aided by a particle mixture made up of electrically charged toner particles and ferromagnetic carrier particles; a second carrier element to which at least one part of the toner particles of the particle mixture are transferred; and a cleaning unit for accepting the particle mixture after the transfer of at least one part of the toner particles to the second carrier element, the cleaning unit accepting, with the aid of the supplied particle mixture, the toner particles present on the first carrier element; and at least one of a first voltage source configured to provide a first potential difference between the toner application unit and the first carrier element, and a second voltage source configured to provide a second potential difference between the cleaning unit and the first carrier element; wherein the electrostatically charged toner particles are electrically positively charged, that the potential of the first carrier element is negative relative to the potential of the toner application unit, and positive relative to the potential of the cleaning unit. 